Measurements in Experiments Chapter 1-2

Numerical Measurements Are used to perform science experiments. Gives number and dimensional unit  Example : 5 m (meters), 15 kg (kilograms), 25 s (seconds)

Dimensional Units SI (Systeme International) is the standard measurement system for science. Three basic dimensions are length, mass, and time. The units for length, mass and time are meter (m), kilogram (kg), and second (s).

SI Prefixes To accommodate the broad range from very large to very small measurements, SI uses prefixes.

SI Prefixes Using these prefixes we are able to build conversion factors from any equivalent relationship.  1 mm = 1 x m When converting, both dimension and units MUST AGREE.  Example: m (length) ≠ kg (mass)

Sample Problem 1A Open Books to pg. 14

Accuracy and Precision Careful measurements are very important in physics. Accuracy – how close to true value  Problems with accuracy are due to error  Human error, method error, instrument error Precision – how exact  Problems with precision are due to limitations  More decimal places, more precise (1.325m is more precise than 1.3m)

Significant Figures Used to indicate precision.

Calculating with Sig Figs

Rules for Rounding

Guided Practice Section Review Pg. 19